Anti-reverse clutch safety device

ABSTRACT

A conventional over-running clutch-type &#39;&#39;&#39;&#39;no back&#39;&#39;&#39;&#39; mechanism normally backstops or grounds out a drive shaft in the event of a load thereon tending to cause reverse wind-up at clutch elements of the mechanism; and the latter is equipped with a safety device which signals the presence of excessive wind up or slip condition. The device is applied coaxially to the mechanism&#39;&#39;s drive shaft, and includes a sprag assembly torqued reversely in response to such undue slip or wind-up. The assembly is interposed radially between an outer rotatable race, and a cylindrical stud providing an inner race, both races being coaxial with the shaft; and the stud is coupled to rotate with the latter in its driving phase, in which the stud over-runs relative to the outer race. When shaft backstopping is in effect the sprag assembly transmits that torque to the outer race; and in response the excessive wind-up or slip, as picked up by the sprag assembly, the latter causes the outer race to rotate a bit. This minor rotation enables a part of the outer race to cammingly close an electric limit switch, thus originating a signal to audibly or visibly alert an attendant.

United States Patent Charchian et al.

[54] ANTI-REVERSE CLUTCH SAFETY DEVICE [72] Inventors: Loris J.Charchlan, Royal Oak; Thaddeus Lech, Warren, both of Mich.

[73] Assignee: Formspray Company, Warren,

Mich.

[221 Filed: Dec. 9, 1970 [21] Appl. No.: 96,359

[52] US. Cl ..l92/30 W, 192/8 R, 192112 B, l92/45.l, ZOO/61.39, 200/153N, 340/271,

, 188/1 A i [51] Int. Cl ..G08b 21/00, Fl6d 41/07, H01h 3/16 [5 Field ofSearch ..192/30 W, 41 A, 45.1, 8R, 192/12 B; 340/271; 81/525; ZOO/61.39,153 N; 188/1 A [56] References Cited UNITED STATES PATENTS 7 2,427,4539/ 1947 Hadley ..200/6l.39 2,743,803 5/1956 Ferris ..l92/4l A 985,9433/1911 Sachs ..200/l53 N 1,307,725 6/1919 Coe ..200/153 N 2,143,550l/1939 Gilbert ..200/6l.39 1,191,973 7/1916 Johnson ..200/61.392,920,156 l/1960 Rice et al ..200/61.39

[ 1 Sept. 26, 1972 3,233,053 2/1966 Parks ..200/61.39

Primary Examiner-Allan D. Hermann AttorneyWhittemore, Hulbert & Belknap57 ABSTRACT mechanisms drive shaft, and includes a sprag assemblytorqued reversely in response to such undue slip or wind-up. Theassembly is interposed radially between an outer rotatable race, and acylindrical stud providing an inner race, both races being'coaxial withthe shaft; and the stud is coupled to rotate with the latter in itsdriving phase, in which the stud over-runs relative to the outer race.When shaft backstopping is in effect the sprag assembly transmits thattorque to the outer race; and in response the excessive wind-up or slip,as picked'up by the sprag assembly, the latter causes the outer race torotate a bit. This minor rotation enables a part of the outer race tocammingly close an electric limit switch, thus originating a signal toaudibly or visibly alert an attendant.

11 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION FIELD Theinvention finds application in any field in which an undue reverse slipor excessive wind-up of a torque transmitting, over-running type clutchor reverse backstopping brake mechanism is apt to be a safety threat orat least a source of inacceptable performance. A typical example, is aninstallation in which a known over-running no-back or anti-reverse unit,whether of a sprag type, a ball and ramp type or a grounding brake shoetype, backstops a an inclined endless belt or chain conveyor. Many otherinstallations will, however, suggest themselves, for example, in theform of signalling equipment on any fixed or'vehicular braked system inwhich brake failure or deterioration is apt to arise.

SUMMARY or THE INVENTION The invention superimposes onto a main drivershaft, as governed by an over-running or other type no-back, a second,similarly over-running type of clutch for the purpose of signalling apartial failure or deterioration at the no-back before it grows toserious proportion. The clutch ispreferably one employing a fullcomplement sprag assembly in the radial space between what amounts to asmall diameter coaxial race extension of the driver shaft and an outerclutch race, a limited rotation of which outer race in response to slipor wind-up at the driver shaft no-back unit has the effect, mechanicallyand electrically, of triggering an alarm circuit for the purposedescribed above.

The interposed signalling clutch assembly or unit is very compact,inexpensively produced, and readily and quickly applied to an existingbackstopped drive shah.

Its inner race member or shaft extension is coupled to the backstoppeddrive shaft and will permit a permissible minor degree of slip orreversewind-up torque of that shaft without tripping the electricalalarm system, but any such reverse effect, for example one indicative ofexcessive main shaft clutch wear, will be detected. A critical value asto the excess is determined in accordance with the setting of a springbiased limit switch trip'ped consequent to a rotation of the outerclutch race of the signalling unit, and signalling audibly or visibly toan attendant is the result. Thus a major wind-up or slip at the no-backto an extent requiring repair or replacement is instantaneously broughtto the attention of the attendant and in an extreme case the signal ismaintained until corrective or manual re-set action is taken. Other moreminor instances are also signalled individually as they arise.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary view partiallybroken away and in vertical section on broken line 1-1 of FIG. 2, thesection in major part being in a plane including the common axis of thebackstopped drive shaft and the safety signalling device applied to theshaft;

FIG. 2 is a fragmentary view in end elevation, as from the right of FIG.I; and

FIG. 3 is a view in transverse radial section along line 3-3 of FIG. 1.

2 DESCRIPTION OF A PREFERRED EMBODIMENT The safety alarm device of theinvention, generally designated by the reference numeral 10, is shown asbeing fixedly mounted upon the external surface of a verticallyelongated rectangular face plate 11, which plate is in turn rigidlysecured, as by four elongated studs 12 and interposed spacers inoutwardly spaced relation to one axial end of a housing 13. The studs 12extend through holes in a housing end plate 14, having threadedengagement in a main housing member 15. The latter encases, and affordsan internal fixed cylindrical brake surface of, an entirely conventionalnoback mechanism, which may typically be of a roller and ramp type, adisc type, a sprag type, an expanding brake shoe type, or the like.Examples are shown and described in the patents to Rasmussen, U.S. Pat.No. 3,200,916 of Aug. 17, 1965, and Kalns, U.S. Pat. No. 3,335,831 ofAug. 15, 1967 (FIGS. 1-5). Many others are old and well-known in theart, hence illustration here is deemed unnecessary. It suffices to statethat in the event of an excess load torque on a shaft driver the excessis grounded out on a fixed brake surface, which for the present purposemay be considered to be represented by the housing member 15. Hencereverse torque is not transmitted in a manner to tend to rotate a drivershaft reversely of its normal direction.

The reference numeral 16 typically designates such a I driver shaft, aspowered from a suitable prime mover (not shown). It is shown as beingrotatively journalled in the axial housing end platelq, being restrainedaxially by an appropriate collar 17 held to the shaft by a set screw 18.Appropriate oil level gauge fittings 19 extend through plate 14 to theinterior of the clutch, these components not being germane to theinvention.

Pursuant to the invention, a small diameter threaded stem member or stud20 is rigidly screwed in a bore 21 of the shaft 16 at the latters axialcenter line, a hex head 22 of the stud 20 bearing tightly against theend of shaft 16, so that the stem member or stud 20 constitutes ineffect, a small diameter axial extension of the shaft rotating unitarilywith the latter. In the event that the shaft is one which does notproject outwardly of housing plate 14, and a collar 17 is not employed,a jam nut 23 (dotted line in FIG. 1) may be threaded on the shank ofstud 20, taking tightly against the end-exposed surface of driver shaft16.

As shown in FIG. 1, shaft stem extension 20 fixedly carries outwardly ofits hex head 22, an axially outwardly opening cup member 24, to theinterior of which an annular torsion transmitting block member 25 of a amedium hard grade rubber is bonded; and cup member 25 is. externallytelescoped with slight radial clearance by a shielding cup member 26suitably fixed on the inner surface of end plate 1 l.

The axial bore of resilient torsion transmitting block 25 fixedlyreceives a coaxial cylindrical stem member 27, which may have a knurledinner end portion 28 forced into the bore of block 25 to effect adriving connection with the latter. The portion 29 of stem member 27 tothe right of plate 11, through an opening in which it extends, is oftrue and externally smooth cylindrical cross section; and this portion29 serves as an inner operating or driver race of an alarm-controllingsprag sub-assembly of the device 10.

This assembly, generally designated by the reference numeral 31, iscoaxially received within a fixed clutch housing 32 of cup-shaped crosssection, including an annular radial wallportion 33 secured by screws(FIG. 3) to the outer wall of plate 11, and a cylindrical, axiallyextending wall portion 34. A ball bearing 35 recessed in the bore ofradial wall portion 33 serves as a journal for the stem portion 29,which portion affords an inner race surface of sprag assembly 31. Aspecially cross-sectioned, manually adjustable member 36 of the spragassembly provides an outer and driven sprag race surface 37 radiallyopposed to the driving race surface at 29 on the stem member 27, beingradially spaced from the latter; and a full complement set of sprags 38is received in the space between the race surfaces 29 and 37.

As best shownin FIG. 3, the sprags 38 are of a wellknown D-shaped crosssection, being energized for engagement between thecoaxial races by apair of conventional annular gartersprings 39. In a driving phase ofoperation of the backstopped main shaft 16, the direction of rotation ofthat shaft; hence of the stern race extension 29, will be counterclockwise, as viewed in FIG. 3; and the extension 29 will freely overrunin that direction the outer race surface 37 and the set of sprags 38,which will bear slidably on the driver race at 29. However, when drivingtorque ceases, the backstopped shaft load will act on the complement ofsprags in the reverse, clockwise direction; and they will,

in normal locked-up sprag-operating fashion, drivingly couple the innerrace 29 with the outer race 37 of clutch assembly 31.

The latter thus becomes subject to the backstopped clockwise-actingtorque, as transmitted from driver shaft 16 through the primary shaftstud extension 20 and resilient torque transmitting block member 25 tothe inner'race member 27 at 29. v

Sprag outer race member 36 has an intermediate diameter bore portionreceiving a small needle bearing 40' to journal member 36 in relation todriver race 29; and the member 36 is also provided with an integral,reduced .diameter reset stem formation 41. This carries at its outeraxial end a kerf or slot 42 to receive a screw driver for resetting thedevice in the event of a slip or wind-up motion, as transmitted throughthe sprag assembly 31, exceeds a'predetermined critical value, as willbe described. The reset stem formation 41 extends through an opening ina cupped protective casing 43 which is secured by screws 43 to the outersurface of the end plate 1 1.

As best shown in FIG. 3, the outer race member 36 of clutch assembly 31'is for the most part cylindrical at its outer largest diameter surface.However, this surface is provided with a V-shaped camming notch 44paralleling the axis of the race surface 37, the notch normallyreceiving nestingly a radially inward head formation 45 of a switchoperating stem 46 which acts in the manner of a cam follower inreference to the camming notch 44 of driver race member 36.

Stem head 45 is slidably guided in the cylindrical radially extendingbore of a generally cylindrical tubular cap 47, which is threadedlyreceived fixedly in a radial opening through the cylindrical wallportion 34 compression spring 49 surrounds the stem 46 within the capbore, acting against and normally urging the stem follower head 45radially inwardly. This head'has a V-shaped nose 50 which is thusnormally springurged into the V-shaped camming notch 44 of race memberwall 34.

A conventional limit switch 52, normally spring biased to open conditionby standard internal means, is threadedly received in an end bore of theguide cap 47 the operating plunger 53 of this switch normally engagingradially inwardly under internal switch spring bias against the radiallyouter end of the operating stem 46. Conventional electrical leads 55 and56 are operatively connected to internal terminals of limit switch 52,which terminals are electrically connected when a predetermined radialmovement of the operating stem 46, under camming shift of its V-nose 50by the clutchrace portion notch 44, exceeds a certain extent. This isdetermined precisely by an appropriate pre-set adjustment of switch 52at the time of installation of the signalling alarm device 10.

Referring to FIG. 1 suitable compressable gasket or packing 57 isinterposed between the inner surface of shielding cup 43 and the housing32 for sprag assembly 31, abutting to the left against a relativelylarge diameter ball bearing58, which constitutes a main journal supportfor the outer race member 36 within the housing 32. The other ballbearing 35 and needle bearing 40 similarly journal the inner race 29.

' The electrical lead 55, 56 are brought externally of the shield cup orcasing 43 through a conventional connector 59, being externallyconnected to an alarm circuit appearing schematically in FIG. 1. Thiscircuit comprises a supply transformer 60 connected to an appropriate120 volt alternating current source, with the secondary side of thetransformer 60 connected by a lead 61 to a contact of a normally closed,manually operated reset switch 62, the lead 55 of limit switch 52tapping into the lead 60. Another transformer secondary lead 63 extendsto a coil terminal of a normally open holding relay 64 controllingganged armature contacts 65 and 64, the former of which is connected toa second contact of reset switch 61. When the contacts 64, 65 areclosed, upon closing of the circuit of limit switch 52, a sub-circuit iscompleted which includes leads 68 and 69 connected to primary inputterminals of the supply transformer 59, the relay contactor 66, and theterminals of a 120 volt visible or audible alarm unit 70 of aconventional nature.

In the operation of the unit 10, its inner race member 29 will normallyoverrun the set of sprags 38 and the outer race member 36 in the counterclockwise direction by the arcuate arrow in FIG. 3, as mentioned above.Under a tendency of clutching slip at the noback mechanism, or of anundue reverse wind-up, this torque factor is imposed in a clockwisedirection (FIG. 3) on the sprag set. Camming notch 44 of outer racemember 36 thus exerts a strong radially outward bias upon the V-nosedhead 45 of operator stem 46,=which force may well be, in a relativelyslight rotation of outer race member 36, adequate to cause closure oflimit switch 52, with at least a momentary completion of the alarmcircuit and a lighting or sounding of the alarm device 70. If acondition of minor slip or wind-up exists, upon its ceasing the built-inspring bias of limit switch 52 may well automatically re-set theoperator member 46 in a radially inward direction, thus automaticallycounter-rotating the outer race member 36 to an original position,whereupon the alarm circuit automatically disconnects.

If, however, the wind up continues and camming force exerted by outerrace 36 continues, and becomes sufficient to rotate the outer race asmuch as a critical value of, say, this will suffice to raise operatingmember or stem 46 enough that its V-nose formation 50 will come to restupon the outer cylindrical surface of race member 36 directly adjoiningthe camming notch formation 44, which cylindrical surface portion thenbecomes a holding formation sustaining the follower head 45 in a fullyraised position. The limit switch 52 then remains locked in a closedcondition; and the alarmcircuit continues energized. A serious conditionof continuing slip or excessive wind-up in to the backstopping no-backis signalled, whereupon the attendant will manually operate the re-setswitch 62 opening the relay circuit of relay 64 and tie-energizing alarmdevice 70. After taking a suitable corrective measure, the attendantwill, using a screw driver, operate the slotted stem'extension 41 of theouter race 36 in a direction to enable the enlarged head 45 of switchoperating stem 46 to re-set radially inwardly into the notch 44, atwhich time the device 10 has been reset to condition for a new operatingcycle.

What is claimed is: V

1. In a load condition indicating device, a unit including a firstrotatable part having means to connect the same for rotation in timedrelation to that of a rotative load sustaining member whose loadcondition is to be tion of one of said parts relative to the other partin the direction reverse of said substantially unitary rotation, saidsecond, driven race part having an external cam formation thereonadjoined by a holding formation, said responsive signal-initiating meanscomprising a follower element engaged with said cam formation andoperated by the latter to initiate a said signal in a conjoint unitaryrotation of said race parts to a predetermined angular extent, aconjoint rotation of second race part beyond said predetermined angularextent causing said follower element to be moved by said cam formationto said holdingformation and held by the latter as so moved.

2. The device of claiml, in which said overrunning clutch assembly is asprag type in which said first and second parts respectively constitutecoaxial driving and driven races, said set of torque-transmittingelements comprising sprags operatively interposed between said races,said assembly permitting substantially free rotation of said first partbeyond the second part in the direction reverse of said substantiallyunitary.rotation in the absence of said rotation.

3. The device of claim 1, in which said signal-initiating means furthercomprises an electric switch operated by said follower element inresponse to said substantially unitary rotation.

4. The device of claim 1, in which said first-named connecting means isin part resilient.

5. The device of claim 5, in which said first-named connecting means isin part resilient.

6. The device of claim 3, in which said first-named connecting means iscoaxial with said first rotatable part and said rotative load sustainingmember.

7. The device of claim 3, in which said first-named connecting means isin part resilient and is coaxial with said first rotatable part and saidrotative load sustaining member.

8. The combination with a clutch mechanism releasably operable intorque-transmitting relation to a rotary member subject toload, of adevice to signal the existence of an overload torque condition asreceived and borne by said member, said device comprising a first racepart rotatable in timed relation to said rotary member, a second racepart coaxial with said first race part, an annular over-running clutchassembly radially interposed between said race parts and releasablycoupling the same for conjoint rotation together under and in therotative direction of said torque, the race parts overrunning rotativelyin the reverse direction, and signalling means including a unit operatedin response to a rotation of said second race part conjointly with thefirst race part to initiate a signal.

9. The combination of claim 8, in which said second race part has anexternal cam formation thereon adjoined by a holding formation, saidsignalling means comprising a follower element engaged with said camformation and operated by the latter to initiate a signal in a conjointunitary-rotation of said race parts to a predetermined angular extent, aconjoint rotation of second race part beyond said predetermined angularextent causing said follower element to be moved by said cam formationto said holding formation and held by the latter as so moved, wherebythe initiated signal is a continuing one.

10. The combination with an anti-reverse feed back clutch mechanismoperable in torque-transmitting relation to a rotary shaft subject toload, of a device to signal the existence of an overload torquecondition as received and borne by said shaft, said device comprising afirst race part rotatable in fixed coaxial relation with said shaft, asecond race part coaxial with said first race part, an annularoverrunning clutch assembly radially interposed between said race partsand releasably coupling the same for conjoint rotation together underand in the rotative direction of the torque overload, the race partsoverrunning rotatively in the reverse direction, and signalling meansincluding an electric switch operated directly in response to a rotationof said second race part conjointly with the first race part to initiatean electrical signal.

11. The combination of claim 10, in which said second race part has anexternal cam formation thereon adjoined by a holding formation, saidsignalling means comprising a follower element engaged with said camformation and operated by the latter to initiate a signal in a conjointunitary rotation of said race parts to a predetermined angular extent, aconjoint rotation of second race part beyond said predetermined angularextent causing said follower element to be moved by said cam formationto said holding formation and held by the latter as so moved, wherebythe operation of said switch continues and the initiated electricalsignal is a continuing one.

UNITED STAT S PATENT @FHQE CER'HFICATE 0F CQEQ'HQN Patent No. 3,693,770Dated segtember 26, 1972 Inventor(s) Loris J. Charchian ahd ThaddeusLech It is certified that error appears in the above-identified patent Iand that said Letters Patent are hereby corrected as shown below:

In the caption, item 73, the spelling of the name of the assignee shouldbe corrected to read "Formsprag" Company.

The words "in the absence of said rotation" should be deleted from thelast line of Claim 2.

In the first line of Claim 5, the. numeral "5" should be changed to2'. Y

Signed and sealed this 24th day of April 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCI-L ALK Attesting OfficerCommissioner of Patents FOPM PO-1050(10-E9) USCOMM-DC 603764 69 s u.sGOVERNMENT PRINTING ornca i969 o-zse-aa-s

1. In a load condition indicating device, a unit including a firstrotatable part having means to connect the same for rotation in timedrelation to that of a rotative load sustaining member whose loadcondition is to be indicated, a second rotatable part, means operativelyconnecting said parts for substantially unitary rotation together to anextent determined by said condition, and means responsive to saidsubstantially unitary rotation of said second part with the first partto initiate a signal indicative of the condition, said partsconnectingmeans being an overrunning clutch assembly in which said first andsecond parts respectively constitute coaxial driving and driven races,and a set of torque-transmitting elements operatively interposed betweensaid races, said assembly permitting substantially free rotation of oneof said parts relative to the other part in the direction reverse ofsaid substantially unitary rotation, said second, driven race parthaving an external cam formation thereon adjoined by a holdingformation, said responsive signal-initiating means comprising a followerelement engaged with said cam formation and operated by the latter toinitiate a said signal in a conjoint unitary rotation of said race partsto a predetermined angular extent, a conjoint rotation of second racepart beyond said predetermined angular extent causing said followerelement to be moved by said cam formation to said holding formation andheld by the latter as so moved.
 2. The device of claim 1, in which saidoverrunning clutch assembly is a sprag type in which said first andsecond parts respectively constitute coaxial driving and driven races,said set of torque-transmitting elements comprising sprags operativelyinterposed between said races, said assembly permitting substantiallyfree rotation of said first part beyond the second part in the directionreverse of said substantially unitary rotation in the absence of saidrotation.
 3. The device of claim 1, in which said signal-initiatingmeans further comprises an electric switch operated by said followerelement in response to said substantially unitary rotation.
 4. Thedevice of claim 1, in which said first-named connecting means is in partresilient.
 5. The device of claim 5, in which said first-namedconnecting means is in part resilient.
 6. The device of claim 3, inwhich said first-named connecting means is coaxial with said firstrotatable part and said rotative load sustaining member.
 7. The deviceof claim 3, in which said first-named connecting means is in partresilient and is coaxial with said first rotatable part and saidrotative load sustaining member.
 8. The combination with a clutchmechanism releasably operable in torque-transmitting relation to arotary member subject to load, of a device to signal the existence of anoverload torque condition as received and borne by said member, saiddevice comprising a first race part rotatable in timed relation to saidrotary member, a second race part coaxial with said first race part, anannular over-running clutch assembly radially interposed between saidrace parts and releasably coupling the same for conjoint rotationtogether under and in the rotative direction of said torque, the raceparts overrunning rotatively in the reverse direction, and signallingmeans including a unit opeRated in response to a rotation of said secondrace part conjointly with the first race part to initiate a signal. 9.The combination of claim 8, in which said second race part has anexternal cam formation thereon adjoined by a holding formation, saidsignalling means comprising a follower element engaged with said camformation and operated by the latter to initiate a signal in a conjointunitary rotation of said race parts to a predetermined angular extent, aconjoint rotation of second race part beyond said predetermined angularextent causing said follower element to be moved by said cam formationto said holding formation and held by the latter as so moved, wherebythe initiated signal is a continuing one.
 10. The combination with ananti-reverse feed back clutch mechanism operable in torque-transmittingrelation to a rotary shaft subject to load, of a device to signal theexistence of an overload torque condition as received and borne by saidshaft, said device comprising a first race part rotatable in fixedcoaxial relation with said shaft, a second race part coaxial with saidfirst race part, an annular overrunning clutch assembly radiallyinterposed between said race parts and releasably coupling the same forconjoint rotation together under and in the rotative direction of thetorque overload, the race parts overrunning rotatively in the reversedirection, and signalling means including an electric switch operateddirectly in response to a rotation of said second race part conjointlywith the first race part to initiate an electrical signal.
 11. Thecombination of claim 10, in which said second race part has an externalcam formation thereon adjoined by a holding formation, said signallingmeans comprising a follower element engaged with said cam formation andoperated by the latter to initiate a signal in a conjoint unitaryrotation of said race parts to a predetermined angular extent, aconjoint rotation of second race part beyond said predetermined angularextent causing said follower element to be moved by said cam formationto said holding formation and held by the latter as so moved, wherebythe operation of said switch continues and the initiated electricalsignal is a continuing one.